Vehicle leveling system

ABSTRACT

A leveling system for a vehicle comprising sprung and unsprung portions, a fluid operated leveling device for selectively varying the attitude between said vehicle portions, a source of actuating fluid, pump means for pumping fluid from said source thereof to said leveling device, a fluid accumulator including means defining first and second variable volume chambers at least in part defining therebetween a third chamber communicable with said fluid source and said leveling device, and means for controlling operation of said pump means in response to volume changes in at least one of said chambers.

0 United States Patent [151 3,653,676 Higginbotham [451 Apr. 4, 1972 5VEHICLE LEVELING SYSTEM 3,539,744 11/1970 Higginbotham ..200/82 [72]Inventor: William W. Higginbotham, Monroe, Mich. p phi1i Goodman [73]Assignee: Monroe Auto Equipment Co., Monroe, A'mmey HamesS Dlckey &P'erce 57 ABSTRACT [22] Filed: 1970 A leveling system for a vehiclecomprising sprung and un- 21 Appl. No.: 21,714 sprung portions, a fluidoperated leveling device for selectively varying the attitude betweensaid vehicle portions, a source Related APllncamn Data of actuatingfluid, pump means for pumping fluid from said [62] Continuation of SerNo 722 506 Jan 8 1968 source thereof to said leveling device, a fluidaccumulator in- No 3 539 744 eluding means defining first and secondvariable volume chambers at least in part defining therebetween a third521 US. Cl ..280/6 P, 280/124 F chamber Communicable with said fluidsome and Said level- [51] Int CL u 17/04 ing device, and means forcontrolling operation of said pump [58] Field of Search "280/6 124200/82 means in response to volume changes in at least one of saidchambers,

[56] References Cited 23 Claims, 13 Drawing Figures UNITED STATESPATENTS Higginbotham ..280/6 PATEHTEnr-PR 41972 SHEET 2 [IF 4PATENTEDAPR 4 1912 W 3 OF 4 3, 653.676

VEHICLE LEVELING SYSTEM RELATED APPLICATIONS This is a continuationapplication of U.S. application, Ser. No. 722,506, now U.S. Pat. No.3,539,744 filed Jan. 8, 1968, for Combination Electrical Switch andFluid Accumulator Chamber.

BACKGROUND OF THE INVENTION During the last several years, the need forgreater load-carrying capacity in automotive vehicles has continuouslyincreased. This need has resulted from various factors such as increasedvehicle dimensions, larger engines, and the more frequent use ofautomobiles for pulling trailers and the like and for carrying as manyas six passengers along with heavy loads such as baggage, merchandiseand sporting equipment. These uses have substantially increased theloads imposed upon the vehicle suspension systems at the rear end of thevehicles, causing a serious reduction in the clearance between the rearaxles of the. vehicles and the frame or body portions thereof. This, ofcourse, has resulted in frequent bottoming or engagement of theseportions of the vehicles when the vehicles are driven over bumpy roadsand the like, thus eliminating to a large extent the effectiveness ofthe vehicle suspension systems. In addition, when the vehicle rear endsare heavily loaded, the front ends of the vehicles are disposedconsiderably above the rear portions thereof, thereby causing thevehicles headlight beams to be directed upwardly and also seriousimpairment of rearward vision. Also, when the rear ends of vehicles aredisposed below the front ends thereof, the vehicles lose a certainamount of stability required for highspeed turns made on modernturnpikes, expressways, toll roads and the like.

The seriousness of these problems has heretofore been recognized in theautomobile industry, as evidenced by the development of a large varietyof auxiliary suspension units which frequently take the form of coilsprings, flat leaf springs, air cylinders and the like; however, it hasbeen found that when such auxiliary suspension components have beenincorporated in existing vehicle suspension systems, the performance andmore particularly the balance of such systems is frequently adverselyaffected. In addition, many of such previously known auxiliary unitshave been difficult to install; have required the use of specialfittings, complex brackets and the like; and have not been universallyapplicable to various designs and makes of vehicles. Also, in manyinstances such auxiliary units have materially affected the attitude ofthe vehicles when they are unloaded, i.e., they frequently raise therear ends of the vehicles relative to the axles thereof, thus adverselyaffecting the appearance of the vehicles and the overall ridecharacteristics thereof when the vehicles are substantially unloaded oronly lightly loaded.

SUMMARY OF THE INVENTION This invention relates generally to a new andimproved vehicle leveling system adapted to automatically maintain thebody portion of a vehicle in a substantially level attitude regardlessof the degree of loading imposed thereon. More particularly, the presentinvention relates to a vehicle leveling system of the above characteradapted to pump a preselected quantity of an actuating fluid to and froman associated leveling mechanism, such as the vehicles shock absorbersor the like, in accordance with preselected changes in the attitude ofthe spring-supported body portion of the vehicle with respect to theunsprung supported axle portion thereof.

It is accordingly a primary object of the present invention to provide anew and improved vehicle leveling system adapted to overcome theheretofore encountered problems associated with heavily loadedautomotive vehicles.

It is another object of the present invention to provide a new andimproved vehicle leveling system of the above character which is adaptedto utilize the power steering fluid or similar source of actuating fluidto cause preselected expansion or contraction of the vehicles shockabsorbers and thereby correct any change in attitude of the rear end ofvehicle body with respect to the rear axle assembly thereof.

It is still another object of the present invention to provide a new andimproved leveling system of the above character which is entirelyautomatic in operation and which is adapted to be used on virtually alltypes of automotive vehicles, thereby providing for universality ofinstallation.

It is still another object of the present invention to provide a new andimproved leveling system of the above character that is extremely stablein operation and which is not prematurely energized when the vehicle isbraking, accelerating or traversing a road bump or the like.

It is a further object of the present invention to provide a new andimproved leveling system of the above character which is durable inoperation and may be easily installed on a vehicle.

It is yet another object of the present invention to provide an improvedleveling system which exhibits relatively low spring ratecharacteristics to reduce frequency of oscillation as the vehicletraverses a road bump or the like.

It is still a further object of the present invention to provide a newand improved leveling system of the above character that is of arelatively simple design, consists of readily available component partsand is therefore economical to commercially manufacture.

Other objects, features and advantages of the present invention willbecome apparent from the following detailed description, taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration ofan exemplary embodiment of the leveling system of the present inventionshown in association with various component members of a conventionalautomotive vehicle or the like;

FIG. 2 is a transverse cross-sectional view of the leveling switchassembly incorporated in the leveling system of the present invention;

FIG. 3 is a transverse cross-sectional view of the portion of a lostmotion assembly associated with the switch assembly illustrated in FIG.2;

FIG. 4 is an enlarged view of a portion of the switch assemblyillustrated in FIG. 2;

FIG. 5 is a view similar to FIG. 4 and illustrates the switch elementportion thereof in a slightly offset position;

FIG. 6 is a transverse cross-sectional view taken along the line 66 ofFIG. 3, with the piston member shown therein displaced slightly;

FIG. 7 is a longitudinal cross-sectional view of the distribution valveassembly incorporated in the leveling system of the present invention;

FIG. 8 is a view similar to FIG. 7 with the loading solenoid thereof inan energized condition;

FIG. 9 is a view similar to FIG. 7 with the unloading solenoid thereofin an energized condition;

FIG. 10 is a longitudinal cross-sectional view of the fluid accumulatorassembly incorporated in the leveling system of the present invention;

FIG. 11 is an enlarged'fragmentary cross-sectional view of a portion ofthe structure illustrated in FIG. 10, as taken substantially along theline 1 1-11 thereof;

FIG. 12 is a schematic view of the loading portion of the electricalcircuitry of the leveling system of the present invention; and

FIG. 13 is a schematic view of the unloading portion of the electricalcircuitry of the leveling system of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT For convenience ofdescription, the terms upper, lower, front, rear, and words of similarimport will have reference to the various assemblies of the levelingsystem of the present invention described hereinafter in detail.Likewise, the terms inner," outer," and derivatives thereof will havereference to the geometric center of such assemblies and the variouscomponent parts thereof.

Referring now in detail to the drawings, a vehicle leveling system 10,in accordance with an exemplary embodiment of the present invention, isshown in operative association with various component members of aconventional automotive vehicle. More particularly and as best seen inFIG. 1 of the drawings, the leveling system is shown in operativeassociation with an automobile power steering system comprising a powersteering unit 12 and a power steering valve mechanism 14 which isattached to one end of the vehicles steering linkage 16 adjacent a powersteering cylinder 18. The leveling system 10 of the present invention isalso shown in association with an automobile battery 20, ignition switch22, and rear axle suspension system comprising an axle assembly 24 and apair of conventional hydraulically expandable shock absorbers 26 and 28..It may be noted that the aforesaid component members 12 through 28 arenot considered to be a material part of the leveling system 10 of thepresent invention and are incorporated herein merely for purposes ofillustrating a typical operative environment of said system.

Generally speaking, the leveling system of the present inventioncomprises three separate but cooperative assemblies which function topump the power steering fluid of the aforesaid power steering system toand from the shock absorbers 26 and 28 to effect raising and lowering ofthe vehicle chassis or body with respect to the axle assembly 24 inresponse to various load conditions imposed upon the vehicle, wherebythe vehicle body is continuously maintained at a substantially levelattitude. The aforesaid assemblies, which are hereinafter described indetail, comprise a leveling switch assembly 30 that functions to sensethe differential attitude between the axle assembly 24 and the vehiclebody, a fluid accumulator assembly 32 which functions to selectivelycommunicate power steering fluid to the aforesaid shock absorbers 26, 28in response to actuation of the leveling switch assembly 30, and adistribution valve assembly 34 which functions to selectively controlthe rate and quantity of power steering fluid transmitted between thepower steering system and the fluid accumulator assembly 32. The valveassembly 34 comprises a pair of solenoid valve members which are adaptedto be electrically energized by power supplied from the vehicleselectrical system, i.e., battery 20, generator, etc., at such time ascertain electrical circuits within the system 10 are closed, at whichtime the power steering fluid is pumped to and allowed to flow from thefluid accumulator assembly 32 and shock absorbers 26, 28, in the mannerhereinafter to be described in detail.

Referring now in detail to FIGS. 1, 2 and 3, the leveling switchassembly 30 is adapted to be mounted on a spring supported portion ofthe automotive vehicle such as the vehicle body adjacent an unsprungportion thereof. In the exemplary embodiment of the present inventionillustrated in FIG. 1, the switch assembly 30 is adapted to be supportedadjacent the rear axle assembly 24 of the vehicle, as for example, by asuitable support bracket 36 mounted within the rear wheel housing (notshown) or the like. The assembly 30 comprises a generally rectangularshaped housing 38 that may be constructed of a die cast or moldedcorrosion-resistant material, such as aluminum, plastic or the like, andwhich defines a central compartment, generally designated by the numeral40. As illustrated in FIG. 3, one side of the compartment 40 is closedby a cover plate 42 which is coextensive of the one side of the housing38 and rigidly secured thereto by suitable screws, bolts or the like 44.Suitable gasket means 45 is interposed between the plate 42 and theadjacent side of the housing 38 to provide a fluid-tight sealtherebetween. Preferably, the support bracket 36 is rigidly secured tothe cover plate 42, as best seen in F IG. 1. The compartment 40comprises three subcompartments or sections, namely, an elongatedcontact and switch element section 46, a circular support section 48,and an orifice section 50. Disposed within the chamber 40 is anelongated switch element, generally designated 52, comprising a centralcylindrical section 54 which is concentrically and rotatably mountedwithin the support section 48 of the compartment 40. Extending upwardlyfrom and integrally connected to the section 54 is a contact engagingarm 56 having a head portion 58 and an intermediate spring arm portion60. Extending in the opposite direction from the arm 56 is a relativelyshort arm 62 which is also integrally connected to the section 54 andmovable in the opposite direction from the aforesaid arm 56 upon pivotalmovement of the switch element 52 relative to the housing 38, as will beapparent. The opposite sides of the orifice section 50 of thecompartment 40 are inclined, as seen at 64 and 66, to prevent anyinterference between the arm 62 and said side walls during the aforesaidpivotal movement.

A pair of terminals 68 and 70 are mounted in the opposite sides of thehousing 38 adjacent the upper end thereof, which terminals have outerportions 72 and 74, respectively, adapted to be connected to suitableelectric circuitry later to be described. The terminals 68 and 70 alsocomprise inner portions 76 and 78, respectively, which extend inwardlyinto the section 46 of the compartment 40 and are adapted to be engagedby a pair of contacts 80 and 82 rigidly secured to the outer sides of apair of cantilever supported contact spring elements 84 and 86,respectively, extending upwardly within the section 46 of thecompartment 40 from an intermediate portion thereof. The lower ends ofthe spring elements 84 and 86 are rigidly secured within the compartment40 by means of a pair of terminal bolts 88 and 90 which have suitablenuts 92 and 94 threadably mounted on their inner ends and have terminalsections 96 and 98, respectively, extending outwardly from the oppositesides of the housing 38 directly below the terminals 68 and 70,respectively. It will be seen that upon pivotal movement of the arm 56of the switch element 52 toward the left or in a counterclockwisedirection in FIG. 2, the head portion 58 thereof will engage the contactspring element 84 and bias the contact member 80 into engagement withthe contact portion 76 of the terminal 68, thereby completing a circuitbetween the terminal bolt 88 and the terminal 68. In a similar manner,upon pivotal movement of the arm 56 of the switch element 52 toward theright, or in a clockwise direction in FIG. 2, the head portion 58 willengage the contact spring element 86 and bias the contact member 82 intoengagement with the contact portion 78 of the terminal 70, therebycompleting a circuit between the terminal 70 and the bolt 90. The headportion 58 of the switch element 52 is formed with a centrallongitudinally extending bore or recess 100 within the upper end ofwhich a ball detent 102 is located. The detent 102 is resiliently urgedupwardly or toward the upper end of the housing 38 by means of asuitable coil spring or the like 104 interposed between the detent 102and the lower end of the recess 100. The upper end of the contactsection 46 of the chamber 40 is formed with a downwardly extending bossportion 106 within which a suitable hemispherical recess is fonned forreceiving a portion of the ball detent 102. The detent 102 is adapted todelay the head portion 58 of the switch element 52 from moving towardeither of the contact spring elements 84 or 86 until the switch element52 is pivoted a predetermined amount relative to the housing 38, forpurposes later to be described.

Means for further delaying movement of the head portion 58 upon pivotalmovement of the switch element 52 within the compartment 40 is achievedthrough the provision of a relatively high viscosity fluid within thesections 46 and 50 of the compartment 40. The fluid is preferably asilicon or equivalent material having a viscosity of from 30,000 to300,000 centistrokes and preferably in the order of 60,000 centistrokes.At such time as the support section 54 of the switch element 52 rotatesor pivots relative to the housing 38, movement of the arm 56 of theswitch element 52 will be resisted by the silicon material disposedwithin the compartment 40. The switch element 52 is preferablyconstructed of a relatively flexible material such as nylon or the likeso that the portion 60 thereof will be sufficiently flexible to providefor the slightly delayed movement of the contact head portion 58 of theelement 52 relative to the support section 54 thereof.

By virtue of the fact that the section 50 of the compartment 40 is alsofilled with the aforesaid silicon material, pivotal movement of theswitch element 52 will also be resisted by the movement of the section62 of the switch element 52 through the compartment section 50.Resistance to movement of the switch element 52 relative to the housing38 is also achieved by means of a variable size orifice located betweenthe lower end of the switch element section 62 and a generallytrapezoidal shape in boss portion 108 fonned on the lower end of thecompartment section 50. More particularly, and as best illustrated inFIGS. 4 and 5, when the lower end of the switch element 52 is insubstantial registry with the top of the boss portion 108, the length ofthe orifice between these two members is represented by the dimension A,and the flow rate of the silicon material within the section 50 from oneside of the switch section 62 to the opposite side thereof will berelatively slow. However, as the lower end of the switch element section62 moves out of registry with the upper end of the boss portion 108, thelength of the orifice therebetween will be decreased to the dimension Bin FIG. 5, whereby the flow rate of the silicon material between theopposite sides of the switch section 62 will be considerably faster. Forreasons which will be described in greater detail in connection with theoperation of the entire leveling system of the present invention, theprovision of the variable size orifice compensates for the change inattitude between the vehicle chassis and the rear axle assembly thereofduring starting and stopping of the vehicle.

As best seen in FIG. 3, the housing 38 is formed with a cylindricalshaped section 110 which is in substantially axial alignment with thesupport section 48 of the compartment 40 and defines a cylindrical bore112 within which an elongated cylindrical actuating shaft 114 isrotatably mounted. The shaft 114 is fixedly secured to the supportsection 54 of the switch element 52 by means of a suitable diametricallyextending retaining pin 116. A conventional O-ring sealing member 118 isdisposed within an annular recess 120 formed circumjacent the supportsection 48 of the compartment 40, and functions to preclude any leakageof the silicon material between the compartment 40 and the bore 112. Theshaft 114 is adapted to be communicable with the axle assembly 24through a plurality of connecting link members 122, 124 and 126 whichare connected together in a manner such that vertical movement of theaxle assembly 24 relative to the vehicle body is transmitted to theswitch assembly 30. For example, the link 122 is fixedly secured at oneend thereof to the axle assembly 24 and at the opposite end thereof tothe lower end of the link 124. The upper end of the link member 124 isin turn pivotably connected to the rearward end of the link 126 so thatupon relative downward or upward movement of the assembly 24, such aswould occur when the vehicle rides over a bump, the link 126 would bepivoted upwardly or downwardly, as indicated by the phantom lines inFIG. 1.

The forward end of the link 126 is adapted to be attached to theoutwardly projecting end of the shaft 114 by means of a lost motionassembly best illustrated in FIG. 3 and generally designated by thenumeral 128. The assembly 128 comprises a housing or casing 130 which isgenerally cylindrical in shape and defines a central cylindrical bore132 which is arranged transversely to the axis of the shaft 114. Thecasing 130 is also formed with a cylindrical bore 134 which intersectsthe aforesaid bore 132 and is adapted to receive the outer end of theshaft 114 therewithin. An outwardly extending sleeve section 136 isformed on one side of the casing 130 circumjacent the bore 134 and isadapted to be received in a suitable annular recess 138 formed aroundthe periphery of the bore 112 at the outer end of the cylindricalsection 110 of the housing 38. A suitable gland nut or the like 140 isthreadably received within a recess 142 formed circumjace'nt the recess138 for retaining the sleeve section 136 within the recess 138 of thehousing 38.

The outer end of the shaft 114 is formed with a recessed portion 144which defines a flat or planar facet 146 that is axially aligned withthe bore 132 in the casing 130. A cylindrical cup-shaped piston orplunger member 148 is reciprocally or slidably disposed within the bore132 and is resiliently urged into engagement with the flat 146 by meansof a coil spring or the like 150 interposed between the back (right)side of the piston member 148 and the right end of the bore 132. Theleft end of the link 126 is rigidly secured to the casing 130 by meansof a suitable screw, bolt or the like 152 which extends through one endof the casing 130 and an aperture 154 in the link 126. The bolt 152 isprovided with a suitable nut 156 and lockwasher 158, as best seen inFIG. 3. An annular boss 160 is integrally formed on the casing 130 andextends through a suitable aperture 162 in the end of link 126 toprevent any relative rotation of this member with respect to the casing130.

The aforedescribed construction is adapted to provide for limited lostmotion or differential movement between the, link 126 and the shaft 114so that the link 126 can pivot upwardly and downwardly relative to thehousing 38 without rotating the shaft 114. More particularly, the casing130 and link 126 rigidly secured thereto are adapted to rotate apreselected amount relative to the shaft 114, whereby the piston member148 will be biased toward the right in FIG. 3 against the resistance ofthe coil spring 150. During such movement of the members 130 and 126,the shaft 114 will not rotate; however, at such time as the spring 150is compressed a predetermined amount, for example, when the casing 130has moved the piston member 148 to the position shown in FIG. 6, thepiston member 148 will exert sufficient force against the flat 146 onthe shaft 114 that any further pivotal movement of the casing 130 andlink 126 will cause the shaft 114 to rotate relative to the housing 38,resulting in the switch element 52 engaging one of the spring elements84 or 86 to cause the contact members 80 or 82 mounted thereon to engageone of the terminal members 78 or 70, as hereinabove described. Theoverall function of the switch assembly 30 will be more clearlyunderstood when the operation thereof is later described in connectionwith the operation of the entire vehicle leveling system 10 of thepresent invention.

Referring now in detail to the construction of the distribution valveassembly 34, as best seen in FIG. 1, the valve assembly 34 iscommunicable with the power steering fluid circuit which circulatespower steering fluid between the power steering unit 12, the powersteering valve mechanism 14, and the accumulator assembly 32. Moreparticularly, the valve assembly 34 is communicable with a pair of fluidconduits 164 and 166, the latter of which extends between the pumpsection 168 of the power steering unit 12 and the assembly 34, and theformer of which extends between the valve assembly 34 and the powersteering valve mechanism 14, whereby the valve assembly 34, whendeenergized, permits normal free fluid flow between the conduits 164 and166. Conversely, when the assembly 34 is appropriately energized, aportion of the fluid normally flowing through the conduits 164, 166 iscommunicated through a conduit 170 which extends longitudinally of thevehicle between the fluid accumulator assembly 32 and the assembly 34.The conduit 170 is communicable through the valve assembly 34 with aconduit 172 extending between the assembly 34 and the reservoir section174 of the power steering unit 12. Other circuitry including a conduit176 is provided for communicating power steering fluid from the valvemechanism 14 back to the power steering unit 12.

Referring now to FIGS. 7 through 9, the valve assembly 34 comprises acentral valve housing 178 which is formed with a pair of substantiallyidentical internally threaded hollow end sections 180 and 182. Theassembly 34 is provided with a pair of electrically energized solenoids,generally designated 184 and 186, which include externally threadedmounting or adaptor sections 188 and 190 that are respectivelythreadably received within the sections 180 and 182 of the housing 178.Suitable O-ring sealing means 191 are preferably provided between theadaptor sections 188, 190 and the sections 180 and 182 of the housing178 to provide fluid-tight joints therebetween. The solenoids 184, 186include external casing portions 192 and 194 enclosing coils 196 and198, respectively, which are of conventional design and function toeffect longitudinal reciprocal movement of a pair of solenoid armatures200 and 202 that are located along the longitudinal axis of the assembly34 within a pair of cylindrical sleeves 204 and 206 mounted within thecoils 196 and 198, respectively. A pair of terminals 208, 210, and 212,214 are located at the opposite ends of the solenoids 184 and 186,respectively, and are adapted to communicate electric current to thesedevices to effect energization thereof, whereby the armatures 200 and202 move longitudinally of the assembly 34 in a manner later to bedescribed. One or more generally L-shaped sheaths 215 may be provided onthe outer ends of the solenoids 184, 186 to protect the terminals 208,210, 212 and 214 thereof. A pair of end plugs 216 and 218 are disposedat the outer ends of the sleeves 204 and 206, respectively, and areprovided with suitable O-ring sealing means 220 and 222 to prevent anyfluid leakage between the interior of the sleeves 204, 206 and theexterior of the assembly 34.

The housing 178 of the valve assembly 34 is formed with four internallythreaded mounting sections 224, 226, 228 and 230, that define bores 232,234, 236 and 238, respectively, adapted to receive suitable fluidfittings (not shown) which communicate the valve assembly 34 with thefluid conduits 166, 164, 172 and 170, respectively. The bore 236 iscommunicable with a downwardly extending fluid passage 240 whichterminates within the housing 178 intermediate the upper and lower sidesthereof. A longitudinally extending fluid passage 242 is communicable atone end thereof with the lower end of the passage 240 and terminates atits opposite end in a valve seat section 244 formed within a cavity 246defined within the end section 182 of the housing 178. The armature 202of the solenoid 186, (hereinafter referred to are the unloading solenoid186 for reasons that will later be apparent) is provided with alongitudinally extending valve member 248 that is threadably mountedwith a suitable axially extending bore 250 formed in the right endthereof. The valve member 248 is normally resiliently engaged with thevalve seat section 244 by means of a coil spring 252 thereby blockingcommunication between the passage 242 and the cavity 246. The spring 252extends coaxially of the right end of the armature 202 within an annularrecess 254 formed within the adaptor section 190 of the unloadingsolenoid 186. The spring 252 bears at one end against an annularshoulder 256 on the adaptor section 190, and at the opposite end againsta suitable retaining or snap-ring 258 mounted on the right end of thearmature 202. Upon energization of the unloading solenoid 186, thearmature 202 will move axially toward the left in FIG. 7 through 9,whereby the valve member 248 will move out of engagement with the valveseat section 244 to permit fluid flow between the fluid passage 242 andthe cavity 246. At such time as the unloading solenoid 186 isdeenergized, the spring 252 will resiliently urge the armature 202toward the right and reengage the valve member 248 with the valve seatsection 244, thereby blocking fluid flow between the passage 242 and thecavity 246.

The bore 230 is communicable at its upper end with an upwardly extendingfluid passage 260 which terminates at a posi tion substantiallyintermediate the upper and lower sides of the housing 178, and iscommunicable with the above described cavity 246 by means of alongitudinally extending passage 262. The passage 260 is alsocommunicable through a longitudinal passage section 264 with a generallycylindrical shaped valve cavity 266 extending longitudinally within thevalve housing 178. Disposed within the left end of the cavity 266 is agenerally cylindrical shaped check valve housing 268 having a radiallyoutwardly extending flange portion 270 which abuts against a radiallyextending shoulder 272 at the left end of the cavity 266. Sealing meansin the form of a conventional O-ring or the like 273 is preferablyprovided between the outer periphery of the flange portion 270 and theinner periphery of the left end of the valve cavity 266, as illustrated.The left end of the housing 268 extends partially within the passagesection 264 and is formed with a central annular bore 274, the right endof which defines a valve seat 276 that is communicable with the interiorof the cavity 266 by means of a relatively small diameter bore 278. Theopposite (left) end of the bore 274 is communicable with the passagesection 264 by means of an opening 280 formed in the left end of thehousing 268. Fluid flow between the cavity 266 and the interior of thehousing 268 is normally blocked by means of a spherical check valvemember 282 which is resiliently urged into engagement with the valveseat 276 by means of a valve spring 284 that is located within the bore274.

Disposed within cavity 266 is an elongated cylindrical valve insertmember, generally designated 286, which defines a uniform diametercylindrical bore 288 extending coaxially of the cavity 266 and havingthe left end of the armature 200 extending centrally within the rightend thereof. Preferably, the insert member 286 is fixedly secured withinthe cavity 266 by being compressed between the flange portion 270 of thecheck valve housing 268 and the left end of the adaptor section 188 ofthe solenoid 184 (hereinafter referred to as the loading solenoid 184for reasons that will later be apparent). The right end of the insertmember 286 is formed with a plurality of circumferentially spacedradially inwardly extending ports or openings, generally designated 290,which communicate the central bore 288 with an annular recess 292defined around the outer periphery of the right end of the member 286.The bore 252 of the housing section 224 is communicable with the annularrecess 292 by means of a fluid passage 294, whereby fluid communicatedto the section 224 is in continuous communication with the interior ofthe bore 288.

The interior of the bore 288 is also communicable with the bore 234 ofthe housing section 226 through an upwardly extending fluid passage 296formed in the valve housing 178, and through an annular recess 298 and aplurality of radially inwardly extending ports or bores, generallydesignated 300, which are formed in the insert member 286 radiallyinwardly from the recess 298. The bore 288 is also communicable with theannular recess 298, and hence with the fluid passage 296, by way of oneor more openings 302 formed in the valve insert member 286 adjacent theports 300, as seen in FIGS. 7 through 9. Fluid flow between the annularrecess 292 and the recess 298 is prevented by means of a suitable O-ringsealing member 304 disposed within an annulus 306 formed around theouter periphery of the insert member 286.

Slidably or reciprocally mounted within the bore 288 is a cylindricalsleeve valve member, generally designated 308, the outer periphery ofwhich slidingly, yet sealingly, engages the periphery of the bore 288.The valve member 308 is formed with a radially inwardly extendingsection 310 at the right end thereof which terminates at its radiallyinner edge adjacent the outer periphery of the left end of the loadingsolenoid armature 200. The valve member 308 is slidably carried upon theleft end of the plunger 200 and is secured thereto by having the section310 thereof compressed between the left end of a helical coil spring312, which extends coaxially around the left end of the armature 200,and a radially outwardly extending snap-ring or the like 314 mounted onthe left end of the armature 200. The right end of the spring 312 bearsagainst an annular disk 316 located in a recess 318 at the left end ofthe adaptor section 188 of the loading solenoid 184. As illustrated, thedisk 316 is formed with a central aperture 320 through which the leftend of the armature 200 extends. The opposite ends of the bore 288 arecommunicable with each other by means of a plurality ofcircumferentially spaced and longitudinally extending ports, generallydesignated 322, formed in the radially inwardly extending section 310 ofthe valve member 308, and fluid communication between the left end ofthe bore 288 and the bore 278 in the check valve housing 268 is adaptedto be blocked by means of a valve member 324 threadably mounted in asuitable bore 326 fonned in the left end of the armature 200, asillustrated in FIGS. 7 and 9.

It will be seen that upon energization of the loading solenoid 184, thearmature 200 will move toward the right, as seen in FIG. 8, whereby thevalve member 324 will move out of engagement with the check valvehousing 268 to provide for fluid communication between the bore 288 andthe bore 274. As the armature 200 thus moves, the sleeve valve 308simultaneously moves toward the right within the valve insert member 286to block the fluid flow through the plurality of ports 300. It will benoted, however, that the valve member 308 does not move into registrywith the openings 302 so that a limited amount of fluid flow is providedbetween the bore 288 and the fluid passage 296. Upon deenergization ofthe loading solenoid 184, the coil spring 312 will bias the armature 200toward the left, whereby the valve member 324 will move into engagementwith the right end of the check valve housing 268 to block fluid flowbetween the bores 273 and 288. Simultaneously, the sleeve valve member308 will move out of registry with the ports 300 to permit fluid flowfrom the interior of the bore 288 to the annular recess 298 through theports 300. A more detailed description of the sequential operation ofthe valve assembly 34 will be given in connection with the descriptionof the overall operation of the leveling system 10 of the presentinvention.

Referring now in detail to the construction of the fluid accumulatorassembly 32, as best seen in FIGS. 10 and 11, the assembly 32 comprisesan elongated cylindrical housing 328 which defines a central accumulatorchamber 330. The opposite ends of the housing 328 are closed by endheader members 332 and 334 that have beveled outer edges 336 and 338,respectively, which enable the ends of the housing 328 to be crimped orsimilarly deformed radially inwardly over the outer edges thereof tofixedly secure the members 332, 334 to the housing 328. Suitable sealingmembers 340 and 342 are disposed within annular recesses 344 and 346formed around the outer peripheries of the header members 332 and 334,respectively, for providing fluid-tight seals at the opposite ends ofthe housing 328. The end header 332 is formed with a threaded bore 348adapted to have a screw, bolt or the like 350 threadably mountedtherewithin for attaching a ground conductor (not shown) to the member332, whereby to ground the accumulator assembly 32 to the vehicle body.The header member 332 is also formed with a central internally threadedbore 352 adapted to threadably receive a mounting section 354 of a gasvalve assembly 356, which assembly 356 is adapted to be used forcommunicating a gaseous substance into the interior of the chamber 330,as will later be described. The header member 334 is also formed with aninternally threaded bore 358 adapted to threadably receive a mountingsection 360 of a gas valve assembly 362 which is substantially identicalin construction to the aforementioned assembly 356 and is also adaptedto communicate a gaseous substance into the interior of the chamber 330.The member 334 is also formed with a central bore 364 adapted to have aterminal screw, bolt or the like 366 inserted therethrough. Moreparticularly, the terminal bolt 366 is formed with a threaded outer(left) end section 368 adapted to have a pair of nuts 370, 372 threadedthereon for securing thereto one of the electrical conductors later tobe described. The bolt 366 is mounted within a pair of dielectricinsulating members 374 and 376 which are interposed between the outerperiphery of the bolt 366 and the inner periphery of the bore 364, asillustrated in FIG. 10. The members 374, 376 are formed with radiallyoutwardly extending flange sections 378 and 380, respectively, which arelocated adjacent the inner and outer sides of the header member 334 toprevent any axial movement of the members 374, 376 relative thereto. Asuitable O-ring sealing member 382 is interposed between the adjacentends of the members 374 and 376 for providing a gas-tight seal withinthe bore 364.

The bolt 366 is adapted to support a pair of terminal clip members 384and 386 within the left end of the housing 328. The members 384, 386 arepreferably constructed of a resilient current conductive material, andare formed with transversely extending mounting sections 388 and 390 atthe left ends thereof. The section 390 of the clip member 386 is formedwith a central bore 392 adapted to have the terminal bolt member 366inserted therethrough, and the section 388 of the clip member 384 isformed with a central bore 394 adapted to have the insulating member 376inserted therethrough, as illustrated in FIG. 10. It will be noted thatthe clip members 384 and 386 are insulated from one another at theirleft ends by the flange section 380 of the member 376. However, themembers 384 and 386 have converging sections 396 and 308, and divergingsections 400 and 402 which define normally engaged face portions 404 and406, respectively. It will be seen that the mounting section 388 of theclip member 384 abuts against the inner side of the header member 334which is grounded to the vehicle chassis through the housing 328, headermember 332 and the ground wire connected thereto by the screw 350.Accordingly, the clip members 384 and 386 normally complete anelectrical circuit between the terminal bolt member 366 and the vehiclechassis, which circuit will be broken at such time as the clip members384, 386 are separated or biased apart in the manner hereinafter to bedescribed.

As illustrated in FIG. 10, a piston assembly, generally designated 408,is slidably or reciprocally mounted within the left end of the housing328. The assembly 408 comprises a generally cup-shaped piston member410, the outer periphery of which is provided with an O-ring sealingmember 412 nested within a suitable annular recess 414 for slidably, butsealingly, engaging the inner periphery of the housing 328. AnotherO-ring member 416 is nested within a second annular recess 418 formedaround the periphery of the piston member 410 adjacent the left endthereof, which O-ring 416 is adapted to resiliently urge a Delrin orsimilar type anti-friction bearing ring 420 that is disposed within therecess 418 radially outwardly toward the inner periphery of the housing328 to provide a slidable fluid-tight seal therebetween. The pistonmember 410 is formed with a central annular recess 422 within which anelongated cylindrical shaft 424 is disposed. The shaft 424 is formedwith a reduced diameter externally threaded section 426 at the left endthereof which is threadably received within a suitable bore 428 locatedin a mounting section 430 that is integrally formed within the recess422, whereby the shaft 424 extends outwardly from the left side of thepiston member 410 coaxially of the housing 328. The shaft 424 is adaptedto support a plunger 432 for reciprocal movement relative to the pistonmember 410, which plunger 430 is formed with a central bore 434 adaptedto receive the outer or left end of the shaft 424, as illustrated inFIG. 10. The plunger 432 is resiliently urged toward the left end of theshaft 424 by means of a helical coil spring 436 which is disposedcircumjacent the right end of the shaft 424 and a portion of themounting section 430 extending coaxially of the shaft 424. Means in theform of a conventional snapring or the like 438 is disposed within therecess 422 and adapted to engage a radially outwardly extending shouldersection 440 formed on the right end of the plunger 432 to limit movementof this member toward the left end of the shaft 424. The left end of theplunger 432 is formed with a longitudinally extending cylindrical endsection 442 which, upon appropriate longitudinal movement of theassembly 408 relative to the housing 328, is adapted to be insertedbetween the face portions 404 and 406 of the clip members 384 and 386 tobreak the electrical circuit normally maintained therebetween.

It will be seen from the above construction that a preselected increasein fluid pressure on the right side of the piston member 410 will movethe assembly 408 toward the left within the housing 328, whereby the endsection 442 of the plunger 432 will engage the clips 384 and 386;however, the

coil spring 436 is selected such that it will be compressed as theplunger 432 initially engages the clips 384, 386 so that the end section442 will not be interposed between the clip members to break the circuittherebetween until such time as the spring 436 is entirely compressedand the piston member 410 moves further toward the left. With thisconstruction, there is a certain amount of differential movement betweenthe plunger 432 and the piston member 410 to enable the latter toreciprocate within the housing 328 without the end section 442 of theplunger 432 breaking the circuit between the clips 384 and 386. Briefly,the purpose for such an arrangement is to prevent the clips 384 and 386from being separated when the vehicle traverses small bumps or similartype irregularities in the road surface. Accordingly, the levelingsystem of the present invention will not be deenergized when there is atemporary change in attitude between the vehicle body with respect tothe axle assembly 24 thereof.

Mounted on the top of the housing 328 is a combination fluid fitting andterminal support member, generally designated by the numeral 444. Asbest seen in FIG. 10, the member 444 is formed with a transverselyextending fluid passage 446 which includes enlarged diameter internallythreaded sections 448 and 450 adapted to receive fluid fittings 452 and454, respectively, which are communicable with a pair of fluid conduits456 and 458, respectively. The opposite ends of the conduits 456 and 458are communicable with the shock absorbers 28 and 26, respectively, in amanner such that when fluid is pumped to or from the shock absorbers 26,28 through the conduits 456 and 458, the shock absorbers will expand orcontract longitudinally to raise or lower the rear end of the vehiclebody with respect to the axial assembly 24, as will later be described.The member 444 is also formed with a generally vertically extending bore460 which intersects the aforedescribed passage 446 and has an elongatedcylindrical terminal rod 462 extending coaxially therethrough. The upperend of the rod 462 is threaded and adapted to receive a suitable nut 464thereon for attaching an electrical conductor later to be described tothe rod 462. An insulating washer 466 is interposed between the nut 464and the upper end of the member 444 for insulating the nut 464 from themember 444. The rod 462 is supported within the bore 460 by means of anannular guide member 468 which is supported upon a shoulder 470 formeddirectly above the intersection of the bore 460 with the passage 446,and by an annular retainer cylinder 472 having an internally threadedbore 474 which is threadedly received upon an intermediate portion ofthe rod 462. Sealing means in the form of a pair of O-rings 476 and 478are interposed between the outer periphery of the cylinder 472 and theinner periphery of the bore 460, and between the outer periphery of therod 462 and the inner periphery of the bore 474, respectively, toprevent any fluid leakage through the upper end of the bore 460 oraround the rod 462. A retaining ring 480 is provided directly above theupper end of the cylinder 472 to lockingly secure the members 468 and472 within the bore 460.

The member 444 is formed with a cylindrical shaped mounting section 480which extends coaxially of the bore 460 and is secured as by welding orthe like within an annular opening 482 formed in the upper end of thehousing 328 intermediate the opposite ends thereof. An annular metalreinforcing ring 484 extends around the inner periphery of the housing328 at a position longitudinally aligned with the opening 482, the ring484 being formed with a suitable opening 486 adapted to receive thelower end of the section 480 of the member 444. It will be seen that thelower end of the rod 462 extends downwardly within the chamber 330 andis adapted to be in contact with the upper end section 488 of agenerally J-shaped spring contact 490 disposed within the housing 328subjacent the member 444. The contact 490, together with an associatedcontact 442, is supported within the chamber 330 by means of an annularretaining ring 494 which is preferably constructed out of plastic or thelike and is formed such that the outer periphery thereof iscontinguously engaged with the inner periphery of the housing 328, asillustrated in FIG. 10. The contacts 490 and 492 are secured to theinner periphery of the retaining ring 494 by means of suitable screws,bolts or the like 496 and 498, and nuts 500 and 502, the former of whichextend through countersunk bores 504 and 506, respectively. The contact492 is formed with a downwardly extending section 508 which engages theinner periphery of the reinforcing ring 484 so that the contact 492 isin electrical communication with the ground wire secured to the housing328 by means of the screw 350. The contacts 490 and 492 are formed withconverging sections 510, 512, and with diverging sections 514, 516,respectively, which define normally engaged face portions 518 and 520.It will be seen that an electrical circuit is normally completed throughthe rod 462. the contacts 490 and 492, the reinforcing ring 486, housing328, end header 332, and the aforesaid ground wire, which circuit willbe broken at such time as the face portions 518 and 520 are separated.

The member 444 is formed with another transversely extending fluidpassage 522 which, as illustrated in FIG. 11, intersects the passage 446and bore 460 and extends outwardly therefrom within a mounting section524 formed on the rearward side of the member 444. The outer end of thepassage 522 is internally threaded and is thereby adapted to receive asuitable fluid fitting 526 which connects the conduit with the assembly32. It will be seen that the power steering fluid pumped through theconduit 170 will flow through the passage 522 into the bore 460 and willthereafter either flow into the housing 328 or through the conduits 456and 458 to the shockabsorbers 26 and 28, as will later be described,

Reciprocally mounted within the right end of the housing 328 is anotherpiston assembly, generally designated 528, which comprises a generallycup-shaped piston member 530, the outer periphery of which slidablyengages the inner periphery of the housing 328. An O-ring sealing member532 is nested within an annular recess 534 formed around the outerperiphery of the piston 530 and is adapted to provide a fluid-tight sealbetween the outer periphery thereof and the inner periphery of thehousing 328. Another O-ring member 536 is nested within a second annularrecess 538 formed around the periphery of the piston member 530 adjacentthe left end thereof, which O-ring 536 is adapted to resiliently urge aDelrin or similar type anti-friction bearing ring 540 that is disposedwithin the recess 536 radially outwardly toward the inner periphery ofthe housing 328 to provide a slidable, yet fluid-tight sealtherebetween. An elongated cylindrical contact engaging rod 542 extendscoaxially within the right end of the housing 328 and is threadablysecured at its right end within an internally threaded bore 544 formedin the left side of the piston member 530. The rod 542 is preferablyconstructed of plastic or similar dielectric material and is adapted tobe inserted between the face portions 518 and 520 of the contacts 490and 492 upon longitudinal movement of the piston assembly 528 toward theleft end of the housing 328. It will be seen that when the rod 542 isinterposed between the face portions 518 and 520, the contacts 490 and492 will be biased apart a sufficient amount to open the electriccircuit between the terminal rod 462 and the above described ground wireconnected to the accumulator assembly 32. Conversely, when the assembly528 moves toward the right end of the housing 328, the rod 542 will movefrom between the face portions 518 and 520 to establish electric contactbetween the members 490 and 492. An annular plastic or similar typespacer ring 546 is disposed within the housing 328 directly on the rightside of the reinforcing ring 484 and is adapted to prevent the pistonassembly 528 from engaging the ring 484 as the assembly 528 moves towardthe left end of the housing 328 during operation of the assembly 32,thereby reducing any noise or vibration which might occur uponengagement of the assembly 528 with the ring 484.

The portion of the housing 328 interjacent the piston assembly 528 andthe end header 332 is adapted to be charged with a gaseous substance toprovide a cushion which resists movement of the assembly 528 toward theright end of the housing 328. Preferably, this portion of the housing328 is filled with compressed nitrogen or a similar inert gas at apressure of approximately 140 p.s.i. In a similar manner, the portion ofthe housing 328 interjacent the end header 334 and the piston assembly408 is also charged with a compressed gas, preferably nitrogen, at apressure of approximately 425 p.s.i., which is adapted to resistmovement of the piston assembly 408 toward the left end of the housing328. It will be seen that when power steering fluid from the vehicle'spower steering unit 12 is pumped through the conduit 170 to the member444, a portion of the fluid will flow through the passage 522 and bore460 into the central portion of the housing 328 defined between thepiston members 410 and 530. The remaining portion of the fluid pumpedthrough the conduit 170 will flow through the conduits 456 and 458 tothe shock absorbers 26 and 28. When the hydraulic pressure within theshock absorbers 26 and 28 exceeds 140 p.s.i. (the pressure of thecompressed nitrogen behind the piston assembly 528), the piston member530 will move to the right within the housing 328 against the resistanceof the compressed nitrogen. Likewise, when the hydraulic pressure withinthe shock absorbers 26 and 28 exceeds 425 p.s.i. (the pressure of thecompressed nitrogen behind the piston assembly 408), the piston member410 will move toward the left end of the housing 328, as will later bedescribed.

Referring now to the electrical circuit incorporated in the levelingsystem of the present invention and in particular to FIG. 12, it will beseen that the terminal 208 of the loading solenoid 184 is connected tothe vehicles ignition switch 22 by means of a suitable conductor 548,the switch 22 in turn being connected by means of a conductor 550 with asource of electrical energy such as the vehicle battery 20 which isgrounded in a conventional manner by a conductor 552. The oppositeterminal 210 of the loading solenoid 184 is adapted to be connected tothe terminal 68 of the switch assembly 30 by means of a suitableconductor 554. The terminal 88 of the switch assembly 30 is connectedthrough a conductor 556 to the terminal bolt 366 mounted in the endheader 334 of the accumulator assembly 32. As above stated, theaccumulator housing 328 is adapted to be grounded by means of a suitableconductor connected to the assembly 32 by the screw 350 (see FIG. 10),which conductor is representatively illustrated in FIG. 13 by theconductor 558. It will be seen from this circuit that the loadingsolenoid 184 is normally not energized, since the contact 80 in theswitch 30 is not engaged with the inner portion 76 of the terminalmember 68. However, assuming that the shaft 114 in the switch assembly30 has been rotated a predetermined amount due to a change in theattitude between the vehicle body and the axle assembly 24, the arm 56will bias the spring element 84 toward the left and thereby engage thecontact member 80 with the terminal member 68 to complete the abovecircuit, resulting in energization of the loading solenoid 184. Assumingthat the ignition switch 22 remains on, this circuit will remain closeduntil either of two things occur, namely, the shaft 114 rotatessufficiently to permit the arm 56 to move toward the right and therebyenable the contact member 80 to move out of engagement with the terminalmember 68 or, the plunger member 432 moves between and separates theclip members 384 and 386 in the accumulator assembly 32.

Referring now to the schematic wiring diagram illustrated in FIG. 13, itwill be seen that the terminal member 212 of the unloading solenoid 186is connected to the ignition switch 22 by a suitable conductor 560,which switch 22 is in turn connected to the vehicle battery by means ofthe aforementioned conductor 550. The opposite terminal 214 of theunloading solenoid 186 is connected to the terminal member 70 of theswitch by means of a suitable conductor 562, and the terminal 90 of theswitch assembly 30 is connected to the upper end of the rod 462 byanother conductor 564. As hereinbefore stated, the rod 462 is normallygrounded through the contacts 490, 492 and housing 328 of theaccumulator assembly 32. The above circuit operates in substantially thesame manner as the circuit described in connection with FIG. 12 in thatthe unloading solenoid 186 normally remains closed due to the fact thatthe contact 82 is not engaged with the terminal member 70 and hence thecircuit is open. Assuming proper rotation of the shaft 114, the arm 56will bias the contact 82 into engagement with the terminal 70 andthereby complete the aforesaid circuit, resulting in energization of theunloading solenoid 186. This circuit will remain closed until the shaft114 rotates in the opposite direction to permit disengagement of thecontact 82 from the terminal member 70, or until the fluid pressurewithin the housing 328 of the accumulator assembly 32 drops toapproximately 150 p.s.i., at which time the compressed nitrogen on theright side of the piston member 530 will bias the rod 542 toward theleft and inter pose the same between the contacts 490 and 492. It may benoted that although the piston member 530 is disposed in the positionwherein the rod 542 is disposed between the contacts 490, 492, there isstill sufficient power steering fluid within the assembly 32 and theconduits 456 and 458 for proper operation of the shock absorbers 26 and28.

To facilitate correlating all of the above described assemblies such asthe leveling switch assembly 30, the fluid accumulator assembly 32 andthe distribution valve assembly 34, an exemplary operational cycle ofthe vehicle leveling system 10 of the present invention will now begiven.

Assuming the initial condition that the vehicle is completely unloadedor only lightly loaded, the body of the vehicle will be in asubstantially level attitude with respect to the axle assembly 24thereof, and the link members 122, 124 and 126 will be in theirrespective positions illustrated by the solid lines in FIG. 1.Accordingly, the shaft 114 and arm 56 will be in the positionsillustrated in FIG. 2 so that the electrical circuits through thecontact and terminal 68, and through the contact 82 and terminal 70 willbe open to prevent energization of the loading solenoid 184 or unloadingsolenoid 186. As best illustrated in FIG. 7, when the unloading solenoid186 is not energized, the coil spring 252 resiliently engages the valvemember 250 with the valve seat section 254 to prevent fluid flow fromthe fluid passage 240, through the cavity 246 and fluid passages 262 tothe passage 260, thereby blocking fluid flow from the reservoir section174 of the power steering unit 12 to the fluid accumulator assembly 32through the fluid conduits 172 and 170. During the time the loadingsolenoid 184 is not energized, the coil spring 312 resiliently urges thearmature 200 toward the left, thereby engaging the valve member 324 withthe right end of the check valve housing 268 to block fluid flow throughthe bore 278. It will be seen that the check valve 282 is resilientlyengaged with the valve seat 276 to also preclude any fluid flow throughthe bore 278. However, power steering fluid may flow from the fluidpassage 294, through the plurality of ports 290, the central bore 288and ports 300 in the insert member 285, into the fluid passage 296,thereby providing for normal fluid flow from the pump section 168 of thepower steering unit 12 through the conduits 166 and 164 to the powersteering valve mechanism 14.

At such time as the vehicle becomes loaded to any appreciable degree,the rear end of the vehicle will be lowered with respect to the axleassembly 24. As this occurs, the link members 122, 124 and 126 will bebiased to the position A indicated in phantom in FIG. 1. Initial pivotalmovement of the link 126 with respect to the switch housing 38 resultsin the casing 130 being rotated simultaneously therewith, therebycausing the piston member 148 to move toward the right in FIG. 3 againstthe resistance of the coil spring 150. After the link 126 and casing 130have rotated a predetermined amount, any further rotational movementthereof due to a change in attitude of the vehicle body with respect tothe axle assembly 24, will cause the shaft 114 to rotate in acounterclockwise direction in FIGS. 2 and 12. As the shaft 114 thusrotates, the switch element 52 will be biased toward the left and thehead portion 58 thereof will engage the spring element 84, resulting inthe contact member 80 engaging the inner portion 76 of the terminal 68.Such movement of the switch member 52 is resisted by the detent 102 andthe viscous silicon fluid disposed within the compartment 40. Also,movement of the switch element 52 within the compartment 40 is resistedby the variable size orifice defined between the lower end of the switchelement section 62 and the boss portion 108 formed in the lower end ofthe compartment 40, as hereinabove described.

Assuming that the vehicles ignition switch 20 is turned on, as thecontact 80 engages the terminal 68, the loading solenoid 184 will beenergized through the electrical circuit consisting of the conductors550, 548, 554 and 556, as hereinabove described in connection with theschematic diagram illustrated in FIG. 12. Upon energization of thesolenoid 184, the armature 200 thereof will move toward the right fromthe position illustrated in FIG. 7 to the position indicated in FIG. 8,thereby biasing the valve member 324 away from the right end of the bore278 to communicate the bore 288 with the interior of the check valvehousing 268, whereby the check valve member 282 will be disengaged fromthe valve seat 276 due to the fluid pressure within the bore 288. As thearmature 200 moves toward the right, the sleeve valve member 308 willmove into registry with the plurality of ports 300 in the valve insertmember to at least partially limit the flow of power steering fluid fromthe bore 288 into the fluid passage 96. When the sleeve valve 308 isdisposed in the position illustrated in FIG. 8, approximately one-thirdof the fluid pumped to the valve assembly 34 is communicated to thevalve mechanism 14 and the remaining fluid flows through the pluralityof ports 322, the bore 274 in the check valve housing 7 268, the fluidpassage 260, and the conduit 170 to the accumulator assembly 32. It willbe seen from the above that upon energization of the loading solenoid184, power steering fluid will flow from the pump section 268 of thepower steering unit 12 to both the power steering valve mechanism 14 andthe accumulator assembly 32 to maintain normal operation of the valvemechanism 14 and to effect predetermined expansion of the shock absorbermembers 26 and 28, as will hereinafter be described.

As best seen in FIGS. and 11, the power steering fluid which is pumpedthrough the conduit 170 flows into the bore 460 of the fluid fitting andterminal support member 444, and thereafter flows downwardly into theinterior of the housing 328. Due to the fact that the pressure of thepower steering fluid flowing into the housing 328 is somewhat greaterthan 140 p.s.i., the pressure of the compressed nitrogen on the rightside of the piston member 530, the entire piston assembly 532 is urgedtoward the right end of the housing 328. It will be noted that undernormal loading conditions, the pressure of the power steering fluidinitially pumped to the accumulator assembly 32 is less than 425 p.s.i.,the pressure of the compressed nitrogen disposed in the housing 328interjacent the piston assembly 408 and the end header member 334, sothat the pressure of the power steering fluid is not sufiicient to biasthe piston assembly 408 toward the left end of the housing 328. Sincethe fluid pressure of the power steering fluid which flows into thehousing 328 is determined by the pressure of the compressed nitrogen atthe opposite ends thereof, at such time as the pressure of the powersteering fluid in the housing 328 reaches a predetermined level, anyfurther fluid pumped from the power steering unit 12 will flow from themember 444 through the conduits 456 and 458 to the shock absorbermembers 28 and 26, respectively, causing the members 26 and 28 tolongitudinally expand and thereby raise the rear end portion of thevehicle with respect to the axle assembly 24 thereof and thereby effectleveling of the vehicle body.

In the event that the vehicle is overloaded, the fluid pressure withinthe housing 328 will exceed 900 psi. due to the relatively high pressurerequired to expand the shock absorber members 26 and 28. Accordingly,the piston assembly 408 will be biased toward the left end of thehousing 328, thereby causing the end section 442 of the plunger 432 tobe interposed between the face portions 404 and 406 of the clips 384 and386 to break the circuit to the loading solenoid 184 and ter minate theflow of power steering fluid to the assembly 32. This, of course,assures that the power steering pump will not operate to pump powersteering fluid to the assembly 32 when the vehicle is overloaded. Asabove stated, there is some differential movement provided between theplunger member 432and the piston member 410 so that as the assembly 408moves toward the left end of the housing 328, the end section 442 of theplunger member 432 will not separate the clips 384 and 386 until thecoil spring 436 has been compressed. Such differential movement betweenthe plunger member 432 and piston member 410 prevents the clips 384 and386 from being separated when there is a temporary pressure increasewithin the chamber 330, as might occur when the vehicle traverses roadbumps or similar surface irregularities in the road which cause amomentary change in attitude in the vehicle body with respect to theaxle assembly 24. Also, the differential movement provided between themembers 432 and 410 prevents the clips 384 and 386 from being separatedwhen there is a change in attitude of the vehicle body with respect tothe axle assembly 24 resulting from acceleration of the vehicle. Inaddition, the viscous silicon fluid within the switch housing 38 isadapted to dampen any movement of the shaft 114 with respect to thelinks 122, 124 and 126 so that the contact is continuously engaged withthe terminal 68 in spite of any momentary changes in the attitude of thevehicle body.

It will be seen from the above description of the operation of theaccumulator assembly 32 that this assembly is adapted to minimize to theextreme the volume of power steering fluid required to expand the shockabsorber members 26 and 28 since the compressed nitrogen in the oppositeends of the housing 328 continuously force the piston assemblies 528 and48 away from the opposite ends thereof, thus forcing the power steeringfluid to the shock absorber members 26, 28. Moreover, the provision ofthe accumulator assembly 32 serves to minimize the spring rate of theshock absorber members 26 and 28 and hence reduce frequency ofoscillation created as the vehicle traverses road bumps and the like.

At such time as the vehicle is unloaded a predetermined amount,resulting in the rear end thereof being elevated with respect to theaxle assembly 24, the link members 122, 124 and 126 will be pivoted tothe position B indicated in phantom in FIG. 1. As the link 126 ispivoted with respect to the switch housing 38, the casing 130 will berotated simultaneously therewith, causing the piston member 148 toinitially move toward the left in FIG. 3 until the left end of thepiston member 148 contiguously engaged the flat 146 on the shaft 114.This, of course, permits the shaft 114 to rotate clockwise in FIG. 2,resulting in the switch element 52 moving out of engagement with thespring element 84 to break the circuit between the contact 80 and theterminal 68, thereby deenergizing the loading solenoid 184. As thesolenoid 184 is thus deenergized, the armature 200 thereof will bebiased from the position indicated in FIG. 8 to the position indicatedin FIGS. 7 and 9 whereby to block the flow of power steering fluid fromthe pump section 168 of the power steering unit 12 to the accumulatorassembly 32. As above stated, when the armature 200 is disposed in theposition indicated in FIGS. 7 and 9, normal free fluid flow is providedbetween the pump section 168 of the power steering unit 12 and the valvemechanism 14, thereby enabling the power steering system to operatenormally.

As the link member 126 is initially pivoted to the position B in FIG. 1,the casing 130 will be rotated with respect to the switch housing 38 asufficient amount to cause the shaft 114 to rotate counterclockwiseuntil the switch element 52 engages the contact 82 with the terminal 70,thereby completing the circuit energizing the unloading solenoid 186, asillustrated in FIG. 13. Energization of the solenoid 186 causes thearmature 202 thereof to move toward the left from the position indicatedin FIGS. 7 and 8 to the position indicated in FIG. 9, thereby biasingthe valve member 250 out of engagement with the valve seat section 244to permit free fluid flow from the fluid passage 260 through the passage262, cavity 246, and passage 242 to the passage 240. Accordingly, fluidwithin the accumulator housing 328 may flow through the conduit 170,valve assembly 34 and conduit 172 to the reservoir section 174 of thepower steering unit 12. The check valve 282 is automatically engagedwith the valve seat 276 by the spring 284, thereby preventing any fluidflow from the conduit 170 into the pump section 168 of the powersteering unit 12 or the valve mechanism 14 of the power steering system.As the power steering fluid is unloaded from the assembly 32 andcommunicated back to the power steering unit 12, the fluid pressurewithin the chamber 328 will decrease, thereby reducing the fluidpressure in the conduits 456 and 458 to permit the shock absorbermembers 26 and 28 to contract a predetermined amount under the influenceof the weight of the vehicle, whereby the body of the vehicle willassume its normal level attitude.

It will be seen from the above that the loading and unloading solenoids184 and 186, respectively, will be selectively energized as the attitudeof the vehicle body is raised or lowered with respect to the axleassembly 24, thereby providing for fluid flow between the power steeringunit 12 and the accumulator assembly 32, and hence to or from the shockabsorber members 26 and 28. When the vehicle is in a substantiallyunloaded or lightly loaded condition, the link members 122, 124 and 126will be disposed in the positions indicated in solid lines in FIG. 1 andhence the switch element 52 will be disposed in the neutral or centralposition illustrated in FIG. 2, whereby the circuits to each of thesolenoids 184 and 186 is open.

It may be noted that when the rear end of the vehicle is jacked up forany reason, the shock absorbers 26, 28 will expand under the influenceof the weight of the axle assembly 24, thereby considerably reducing thepressure within the members 26, 28. As this occurs, the fluid pressurewithin the central portion of the accumulator housing 328 decreasesaccordingly, resulting in the piston assembly 528 moving toward thecenter of the housing 328 and engaging and separating the members 490and 492, thereby deenergizing the solenoid 186 and assuring that thepower steering fluid within the system will not all be communicated backto the power steering system.

Although particular reference has been made herein to the levelingsystem 10 of the present invention being operatively associated with thepower steering system and shock absorbers of an automotive vehicle, itwill be noted that the present invention is not intended to be limitedto such a combination since the leveling system 10 is adapted to operateeffectively with various sources of pressurized fluid other than a powersteering system, such as an auxiliary pump for pumping transmissionfluid to and from the accumulator assembly. Furthermore, it will benoted that the raising and lowering of the vehicle body with respect tothe axle assembly thereof may be accomplished by any one of a number ofwell known fluid pressure expandable devices other than hydraulic shockabsorbers, for example, conventional hydraulically actuated piston andcylinder assemblies or the like. In addition, it will be appreciatedthat the leveling system 10 of the present invention may be providedwith manually actuable switch means adapted to be located on thedashboard or instrument panel of the vehicle and function to eithersupplement or replace the switch assembly 30. For example, a suitable3-position switch could be used in lieu of or to supplement the assembly30 and adapted to be manually actuated to a first or off positionwherein both of the solenoids 184 and 186 are deenergized, to a secondposition wherein the loading solenoid 184 is energized to effectexpansion of the shock absorbers 26, 28 and hence elevation of the rearend of the vehicle body, or to a third position wherein the unloadingsolenoid 186 is energized to effect contraction of the members 26, 28and hence lowering of the rear end of the vehicle body. As anotherpossible alternative, it is contemplated that the distribution valveassembly 34 may be modified slightly whereby the valve members 248, 308and 324 are movable within the valve housing 178 in response toactuation of a mechanical linkage, for example, a flexible cable or thelike, extending between the valve assembly 34 and a suitable actuatinglever mounted on the instrument panel of the vehicle.

While it will be apparent that the exemplary embodiment hereinillustrated is well calculated to fulfill the objects above stated, itwill be appreciated that the leveling system 10 of the present inventionis susceptible to modification, variation and change without departmentfrom the proper scope or fair meaning of the subjoined claims.

I claim:

1. In combination in a leveling system for a vehicle comprising sprungand unsprung portions,

a fluid operated leveling device for selectively varying the attitudebetween said vehicle portions,

a source of actuating fluid,

pump means for pumping fluid from said source thereof to said levelingdevice,

a fluid accumulator including means defining first and second variablevolume chambers at least in part defining therebetween a third chambercommunicable with said fluid source and said leveling device, and

means for controlling operation of said pump means in response to volumechanges in at least one of said chambers.

2. The combination as set forth in claim 1 which includes means forpermitting the volume of one of said variable volume chambers todecrease in response to an increase in fluid pressure in said thirdchamber.

3. The combination as set forth in claim 1 which includes movablepartition means at least in part defining one of said chambers.

4. The combination as set forth in claim 2 wherein said last mentionedmeans comprises a compressible fluid.

5. The combination as set forth in claim 4 wherein said compressiblefluid comprises a pressurized gas.

6. The combination as set forth in claim 1 which includes first andsecond compressible fluids disposed in said first and second variablevolume chambers, respectively.

7. The combination as set forth in claim 6 wherein said first and secondfluids are at different pressures.

8. The combination as set forth in claim 1 wherein said fluidaccumulator comprises housing means and first and second movablepartition means disposed interiorly of said housing and defining saidchambers therewith.

9. The combination as set forth in claim 8 wherein said housing is of agenerally cylindrical configuration and which includes first and secondpartition means movable interiorly of said housing and definingtherewith said first, second and third chambers, with said third chamberbeing located between said first and second chambers.

10. The combination as set forth in claim 9 wherein said partition meansincludes at least one piston member longitudinally slidable within saidcylindrical housing.

11. The combination as set forth in claim 8 which includes meansresponsive to movement of one of said movable partition means forcontrolling an electrical circuit to said pump means.

12. The combination as set forth in claim 7 which includes means fordeenergizing said pump means when the pressure in said third chamberexceeds the pressure in one of said variable volume chambers.

13. The combination as set forth in claim 7 which includes means fordeenergizing said pump means when the pressure in one of said variablevolume chambers exceeds the pressure in said third chamber.

14. The combination as set forth in claim 10 which includes a pair oflongitudinally slidable pistons in said housing, one of said pistonsdefining with said housing one of said variable chambers and the otherof said pistons defining with said housing the other of said variablevolume chambers, with both of said pistons defining with said housingsaid third chamber,

wherein said first and second chambers are filled with pressurized fluidat different pressures, and which includes first and second pump controlmeans operable in response to movement of said pistons, whereby when thepressure in said third chamber exceeds the pressure in said firstchamber, said pump means will be deactuated, and when the pressure insaid second chamber exceeds the pressure in said third chamber said pumpmeans will be deactuated.

15. In combination in a vehicle leveling system including a fluidoperated leveling device, a source of actuating fluid and meanscommunicating fluid between the source thereof and the leveling device,

a fluid accumulator including means defining first and second variablevolume chambers at least in part defining therebetween a third chambercommunicable with said fluid source and said leveling device, and

means for permitting the volume of one of said variable volume chambersto decrease in response to an increase in fluid pressure in said thirdchamber.

16. The combination as set forth in claim which includes partition meansat least in part defining one of said chambers.

17. The combination as set forth in claim 15 wherein said last mentionedmeans comprises a compressible fluid.

18. The combination as set forth in claim 17 wherein said compressiblefluid comprises a pressurized gas.

19. The combination as set forth in claim 15 which includes first andsecond compressible fluids disposed in said first and second variablevolume chambers.

20. The combination as set forth in claim 19 wherein said first andsecond fluids are at different pressures.

21. The combination as set forth in claim 15 wherein said fluidaccumulator comprises housing means and first and second movablepartition means disposed interiorly of said housing and defining saidchambers therewith.

22. The combination as set forth in claim 21 wherein said housing is ofa generally cylindrical configuration and which includes first andsecond partition means movable interiorly of said housing and definingtherewith said first, second and third chambers, with said third chamberbeing located between said first and second chambers.

23. The combination as set forth in claim 22 wherein said partitionmeans includes at least one piston member longitudinally slidable withinsaid housing.

1. In combination in a leveling system for a vehicle comprising sprungand unsprung portions, a fluid operated leveling device for selectivelyvarying the attitude between said vehicle portions, a source ofactuating fluid, pump means for pumping fluid from said source thereofto said leveling device, a fluid accumulator including means definingfirst and second variable volume chambers at least in part definingtherebetween a third chamber communicable with said fluid source andsaid leveling device, and means for controlling operation of said pumpmeans in response to volume changes in at least one of said chambers. 2.The combination as set forth in claim 1 which includes means forpermitting the volume of one of said variable volume chambers todecrease in response to an increase in fluid pressure in said thirdchamber.
 3. The combination as set forth in claim 1 which includesmovable partition means at least in part defining one of said chambers.4. The combination as set forth in claim 2 wherein said last mentionedmeans comprises a compressible fluid.
 5. The combination as set forth inclaim 4 wherein said compressible fluid comprises a pressurized gas. 6.The combination as set forth in claim 1 which includes first and secondcompressible fluids disposed in said first and second variable volumechambers, respectively.
 7. The combination as set forth in claim 6wherein said first and second fluids are at different pressures.
 8. Thecombination as set forth in claim 1 wherein said fluid accumulatorcomprises housing means and first and second movable partition meansdisposed interiorly of said housing and defining said chamberstherewith.
 9. The combination as set forth in claim 8 wherein saidhousing is of a generally cylindricaL configuration and which includesfirst and second partition means movable interiorly of said housing anddefining therewith said first, second and third chambers, with saidthird chamber being located between said first and second chambers. 10.The combination as set forth in claim 9 wherein said partition meansincludes at least one piston member longitudinally slidable within saidcylindrical housing.
 11. The combination as set forth in claim 8 whichincludes means responsive to movement of one of said movable partitionmeans for controlling an electrical circuit to said pump means.
 12. Thecombination as set forth in claim 7 which includes means fordeenergizing said pump means when the pressure in said third chamberexceeds the pressure in one of said variable volume chambers.
 13. Thecombination as set forth in claim 7 which includes means fordeenergizing said pump means when the pressure in one of said variablevolume chambers exceeds the pressure in said third chamber.
 14. Thecombination as set forth in claim 10 which includes a pair oflongitudinally slidable pistons in said housing, one of said pistonsdefining with said housing one of said variable chambers and the otherof said pistons defining with said housing the other of said variablevolume chambers, with both of said pistons defining with said housingsaid third chamber, wherein said first and second chambers are filledwith pressurized fluid at different pressures, and which includes firstand second pump control means operable in response to movement of saidpistons, whereby when the pressure in said third chamber exceeds thepressure in said first chamber, said pump means will be deactuated, andwhen the pressure in said second chamber exceeds the pressure in saidthird chamber said pump means will be deactuated.
 15. In combination ina vehicle leveling system including a fluid operated leveling device, asource of actuating fluid and means communicating fluid between thesource thereof and the leveling device, a fluid accumulator includingmeans defining first and second variable volume chambers at least inpart defining therebetween a third chamber communicable with said fluidsource and said leveling device, and means for permitting the volume ofone of said variable volume chambers to decrease in response to anincrease in fluid pressure in said third chamber.
 16. The combination asset forth in claim 15 which includes partition means at least in partdefining one of said chambers.
 17. The combination as set forth in claim15 wherein said last mentioned means comprises a compressible fluid. 18.The combination as set forth in claim 17 wherein said compressible fluidcomprises a pressurized gas.
 19. The combination as set forth in claim15 which includes first and second compressible fluids disposed in saidfirst and second variable volume chambers.
 20. The combination as setforth in claim 19 wherein said first and second fluids are at differentpressures.
 21. The combination as set forth in claim 15 wherein saidfluid accumulator comprises housing means and first and second movablepartition means disposed interiorly of said housing and defining saidchambers therewith.
 22. The combination as set forth in claim 21 whereinsaid housing is of a generally cylindrical configuration and whichincludes first and second partition means movable interiorly of saidhousing and defining therewith said first, second and third chambers,with said third chamber being located between said first and secondchambers.
 23. The combination as set forth in claim 22 wherein saidpartition means includes at least one piston member longitudinallyslidable within said housing.